Semiconductor fabrication processes have been developed that permit the integration of very large numbers of transistors, diodes, and other circuit elements onto a single integrated circuit. Such integrated circuits generally require large numbers of electrical connections to receive inputs and supply outputs. Because these integrated circuits are generally very small, the required input/output electrical connections on the integrated circuit are both numerous and densely spaced.
A significant problem in the use of integrated circuits is packaging the integrated circuit in such a way as to electrically connect to the many, densely spaced input/output electrical connections. If the input/output electrical connections must be spread out to permit electrical connections to other integrated circuits, other circuits or circuit components such as printed circuit boards, then much of the advantage of integrated circuit miniaturization is lost.
One method of packaging integrated circuits for electrical connection to a printed circuit board is the so-called ball grid array (BGA) package. A BGA package includes a semiconductor die (an integrated circuit) that is attached to a substrate. Electrical connections are made from the die to the substrate with bond wires that are attached to bond pads provided on the die and the substrate. The bond pads on the substrate are electrically connected to an array of solder balls or bumps, and these solder balls are used to bond and make electrical connection to the printed circuit board. BGA packages are described in, for example, Tsuji et al., U.S. Pat. No. 5,930,603, Tsunoda et al., U.S. Pat. No. 5,914,531, and Tsuji et al., U.S. Pat. No. 5,293,072.
Not only are BGA packages more compact than other packages, BGA packaged devices generally have superior thermal and electrical properties. The solder balls provide an excellent thermal path for the removal of heat from the semiconductor die as well as providing low resistance, low inductance electrical connections.
BGA packages have several drawbacks. For example, soldering a BGA packaged device to a printed circuit board can require precise soldering process control. Accordingly, improved packages, packaging methods, and packaging apparatus are needed.